With an Arduino Uno, you can get 9615 samples per second from an analog input, and do the data processing at the same time. That's more than enough to reliably detect a peak. For this, you have to set the ADC to "free running mode" and do the processing in the ADC interrupt service routine. Se this answer for a detailed explanation and code.
Oh, and instead of peak detection, you could just integrate your signal. That should be simpler, and simple is good for interrupt-driven data processing.